Sensitivity of flood loss estimates to building representation and flow depth attribution methods in micro-scale flood modelling

Thanks to modelling advances and the increase in computational resources in recent years, it is now feasible to perform 2-D urban flood simulations at very high spatial resolutions and to conduct flood risk assessments at the scale of single buildings. In this study, we explore the sensitivity of flood loss estimates obtained in such micro-scale analyses to the spatial representation of the buildings in the 2D flood inundation model and to the hazard attribution methods in the flood loss model. The results show that building representation has a limited effect on the exposure values (i.e. the number of elements at risk), but can have a significant impact on the hazard values attributed to the buildings. On the other hand, the two methods for hazard attribution tested in this work result in remarkably different flood loss estimates. The sensitivity of the predicted flood losses to the attribution method is comparable to the one associated with the vulnerability curve. The findings highlight the need for incorporating these sources of uncertainty into micro-scale flood risk prediction methodologies.     

Climate change risks for severe storms in developing countries in the context of poverty and inequality in Cambodia

Least developed countries are generally regarded as particularly sensitive to climate change due to among other vulnerable locations and low adaptation capabilities. In the present study, we address climate change hazards in least developed countries by presenting a methodological framework, which is suitable for the estimation damage costs as a function of risk aversion, equality, income distribution and climate scenario using state-of-the-art climate model projections. As a case study, the methodology is applied to study severe storms in Cambodia based on two future climate scenarios and data on historical damages from storm events, which are used as a proxy in performing a sensitivity analysis on all input parameters. For the assumptions and parameter ranges used here, the study shows a high sensitivity to the income distribution (reflected by discount rates) and risk aversion and smaller effects from equality measures and extreme wind climate scenario. We emphasize that the assumptions on risk aversion reflecting consumption smoothing possibilities of low-income households clearly depicts that climate risks can be particularly high as a consequence of poverty and therefore recommend that context-specific vulnerabilities and equity concerns in climate risk studies should be included when making assessments for least developed countries.     

Did the transition to plate tectonics cause Neoproterozoic Snowball Earth?

When Earth's tectonic style transitioned from stagnant lid (single plate) to the modern episode of plate tectonics is important but unresolved, and all lines of evidence should be considered, including the climate record. The transition should have disturbed the oceans and atmosphere by redistributing continents, increasing explosive arc volcanism, stimulating mantle plumes and disrupting climate equilibrium established by the previous balance of silicate‐weathering greenhouse gas feedbacks. Formation of subduction zones would redistribute mass sufficiently to cause true polar wander if the subducted slabs were added in the upper mantle at intermediate to high latitudes. The Neoproterozoic Snowball Earth climate crisis may reflect this transition. The transition to plate tectonics is compatible with nearly all proposed geodynamic and oceanographic triggers for Neoproterozoic Snowball Earth events, and could also have contributed to biological triggers. Only extraterrestrial triggers cannot be reconciled with the hypothesis that the Neoproterozoic climate crisis was caused by a prolonged (200–250 m.y.) transition to plate tectonics.     

Optical spectroscopy of two overlapping, flux-density-limited samples of radio sources in the North Ecliptic Cap, selected at 38 and 151 MHz

We present the results of optical spectroscopy of two flux-density-limited samples of radio sources selected at frequencies of 38 and 151 MHz in the same region around the North Ecliptic Cap, the 8C-NEC and 7C- iii samples respectively. Both samples are selected at flux density levels ≈20 times fainter than samples based on the 3C catalogue. They are amongst the first low-frequency selected samples with no spectral or angular size selection for which almost complete redshift information has been obtained, and contain many of the lowest-luminosity z >2 radio galaxies so far discovered. They will therefore provide a valuable resource for understanding the cosmic evolution of radio sources and their hosts and environments. The 151-MHz 7C- iii sample is selected to have S ₁₅₁≥0.5 Jy and is the more spectroscopically complete; out of 54 radio sources fairly reliable redshifts have been obtained for 44 objects. The 8C sample has a flux limit of S ₃₈≥1.3 Jy and contains 58 sources of which 46 have fairly reliable redshifts. We discuss possible biases in the observed redshift distribution, and some interesting individual objects, including a number of cases of probable gravitational lensing. Using the 8C-NEC and 7C- iii samples in conjunction, we form the first sample selected on low-frequency flux in the rest-frame of the source, rather than the usual selection on flux density in the observed frame. This allows us to remove the bias associated with an increasing rest-frame selection frequency with redshift. We investigate the difference this selection makes to correlations of radio source properties with redshift and luminosity by comparing the results from traditional flux-density selection with our new method. We show in particular that flux-density-based selection leads to an overestimate of the steepness of the correlation of radio source size with redshift.     

Comparing crustal and mantle fabric from the North American craton using magnetics and seismic anisotropy

A central target in Earth sciences is the study of deformation at various depth levels within the Earth. Seismology has offered a remarkable tool for doing this via seismic anisotropy. It is however not always clear how to interpret those observations. A question of interest is to understand the relation between the deformation of the mantle and the crust, and in studying the relation between the two. Mantle deformation is expressed in seismic anisotropy. In this paper we seek an objective way of extracting information about crustal fabric as well, to be able to compare with seismic anisotropy. The magnetization of crustal rocks offers an attractive possibility for doing this. We thus explore the use of magnetic data, and we compare magnetic crustal fabric orientation with mantle fabric observations from seismic anisotropy. We apply our technique to the North American craton for which we have an excellent magnetic dataset, and we show that there is a clear relation between crustal and mantle fabric for the cratonic region. This has important implications for crustal formation, and for interpreting seismic anisotropy observations.     

An ArcGIS® Approach to Include Tectonic Structures in Point Data Regionalization

Point data derived from drilling logs must often be regionalized. However, aquifers may show discontinuous surface structures, such as the offset of an aquitard caused by tectonic faults. One main challenge has been to incorporate these structures into the regionalization process of point data. We combined ordinary kriging and inverse distance weighted (IDW) interpolation to account for neotectonic structures in the regionalization process. The study area chosen to test this approach is the largest porous aquifer in Austria. It consists of three basins formed by neotectonic events and delimited by steep faults with a vertical offset of the aquitard up to 70 m within very short distances. First, ordinary kriging was used to incorporate the characteristic spatial variability of the aquitard location by means of a variogram. The tectonic faults could be included into the regionalization process by using breaklines with buffer zones. All data points inside the buffer were deleted. Last, IDW was performed, resulting in an aquitard map representing the discontinuous surface structures. This approach enables one to account for such surfaces using the standard software package ArcGIS^®; therefore, it could be adopted in many practical applications.     

Form induced stresses over rough gravel-beds

This paper presents an analysis of spatial flow heterogeneity over rough gravel beds for shallow flows in terms of form induced stresses. Data from experiments specifically designed with the intention to analyze the flow data with the double-averaging methodology are used to investigate the nature of form induced stresses. It is shown that spatial flow heterogeneity is small at greater distances to the roughness tops (z ₁₀₀), increases slightly towards z ₁₀₀, and increases significantly below z ₁₀₀. Form induced stresses determined over the same bed and with the same slope are found to be independent of discharge. The influence of the number of measuring verticals on the magnitude of form induced stresses is discussed. The distributions of form induced stresses ?<?~w> are used to define the geodetic level of the roughness crest for rough, irregular beds from hydraulic data.     

Ferromagnetic resonance and magnetic characteristics of intact magnetosome chains in Magnetospirillum gryphiswaldense

The magnetic characteristics of intact magnetosome chains in Magnetospirillum gryphiswaldense bacteria were investigated by means of static and dynamic magnetic analyses and ferromagnetic resonance spectroscopy. The nano-sized magnetosomes are generally in a stable single-domain state, but magnetosomes smaller than 30 nm characteristic of superparamagnetic magnetite particles were also found. Alternating current (AC) susceptibility indicates that all magnetosomes are blocked below 150 K. At room temperature the anisotropy of M. gryphiswaldense is dominated by the shape of the magnetosome chains. Low-temperature ferromagnetic resonance (FMR) spectroscopy indicates that this dominant shape anisotropy can affect the detection of the Verwey transition at 100 K. The static and dynamic magnetic analyses show that the Verwey transition is smeared and that our magnetotactic bacteria fail the Moskowitz test. This failure is explained by the biomineralization of non-stoichiometric magnetosomes. This interpretation is based on the increase in high-field susceptibility and the distinct peak in the out-of-phase component of the AC susceptibility below 50 K. These results are attributed to freezing of spins associated with defect structures in the core and at the surface of nano-sized magnetosomes. The results obtained from M. gryphiswaldense demonstrate that intrinsic properties of nano-sized magnetosomes are significantly influenced by non-stoichiometry and by the anisotropy excited from their arrangement in the bacteria.